Phosphorylation of Pax2 by the c-Jun N-terminal Kinase and Enhanced Pax2-dependent Transcription Activation

Abstract

The Pax family of genes encodes transcription factors with conserved DNA binding motifs that are required for embryonic development of a variety of tissues in Drosophila, mouse, and humans. In vertebrates, Pax genes can be subdivided into classes based on similar features and embryonic expression patterns (1). The Pax2/5/8 subfamily is characterized by an amino-terminal-paired domain, a conserved octapeptide sequence with similarity to the engrailed homology domain (EH-1), and a partial-paired type homeobox. Pax2/5/8 proteins are transcription regulators that bind DNA via the amino-terminal-paired domain, whereas the carboxyl-terminal region is required for transactivation of target genes (2, 3).In mouse and man, the Pax2 gene is essential for the development of the kidneys (4), optic cup, and inner ear (5). Pax2 encodes at least two alternatively spliced messages that produce proteins of 392 and 415 amino acids, differing only by a 23 amino acid insertion (6). Genes known to be up-regulated by Pax2 include WT1 (7) and gdnf (8) in the developing kidney and engrailed-2 (9) in the developing hindbrain. In transfected cells, transcription activation requires the Pax2 carboxyl-terminal domain that is rich in serine and threonine residues, which may be potential sites for phosphorylation. In the zebrafish Pax6 protein, the carboxyl-terminal transactivation domain is phosphorylated at multiple serine residues by the mitogen-activated protein kinases (MAPK) 1 p38 MAPK and ERK1/2 to increase the transactivation potential (10). Of the Pax2/5/8 subfamily, only Pax8 has been studied with respect to phosphorylation, though it is not clear which kinases are involved (11). MAP kinase cascades are involved in transmitting signals generated at the cell surface into the cytosol and nucleus and consist of three sequentially acting enzymes: a MAP kinase, an upstream MAP kinase kinase (MEK), and a MEK kinase (MEKK) (12, 13). The extracellular signal-regulated kinase 1/2 (ERK 1/2), the c-Jun N-terminal kinase/stress-activated protein kinases (JNK/SAPK), or the p38MAP kinases, can translocate to the nucleus and subsequentely phosphorylate a variety of transcription factors. MEKK1 phosphorylates MKK4/MKK7 to activate JNK but can also activate ERK and p38 MAPK in transfected cells.This report addresses the phosphorylation state of the Pax2 protein and its ability to activate transcription. We show that the carboxyl-terminal activation domain is phosphorylated at serine and threonine residues and that Pax2 phosphorylation is coincident with the enhanced ability to transactivate a reporter gene. Pax2 is a substrate for the c-Jun N-terminal kinase (JNK) but, unlike Pax6, is not phosphorylated by ERK or p38 MAPK. Activation of JNK by either the upstream kinases MEKK1 or DLK or by expression of Wnt signaling proteins increases Pax2 phosphorylation and enhances the Pax2 transactivation potential. The data point to an important role for JNK in modifying the Pax2 transactivation domain and stimulating Pax2-dependent gene expression. MATERIALS ...

Molecular regulation of kidney development: is the answer blowing in the Wnt?

“…In fact, work performed by Osafune et al suggested that the PCP pathway was required in the mesenchyme downstream of Wnt4 during tubule formation and that canonical signaling actually inhibited Wnt4 activity [56]. This was consistent with results obtained by Cai et al, showing that both Wnt4 and Wnt11 could stimulate Jnk activity and that this activated Pax-2, a transcription factor required for multiple aspects of kidney development [63].…”

B Cell Receptor-ERK1/2 Signal Cancels PAX5-Dependent Repression of BLIMP1 through PAX5 Phosphorylation: A Mechanism of Antigen-Triggering Plasma Cell Differentiation

“…PAX2 is phosphorylated by JNK at the transactivation domain (29), and both ERK1/2 and When BCR signal is induced by Ag, ERK1/2 signal activation and PAX5 phosphorylation occur simultaneously, and repression of BLIMP1 is attenuated by PAX5 phosphorylation (middle). Once BLIMP1 is expressed, it suppresses PAX5 (right).…”

Genetic association between PAX2 and mullerian duct anomalies in Han Chinese females

“…Early studies showed that the Pax2 protein could interact with some repressor proteins to change the positive regulators to negative during the period of transcription [28]. In recent works, scholars identified that the Pax2 transactivation domain is phosphorylated by the c-Jun N-terminal kinase (JNK) [29]. Research proves that the JNK can regulate downstream of the WNT signaling pathway, which is essential for the development of female reproductive ducts [30].…”